Hardstatus issue with current screen, gnome-terminal

[Micah Cowan]

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There's a bug I've been looking into, where the hardstatus line at the
bottom of the screen isn't updating properly when using the "autoaka"
("SEARCH|NAME") feature of the shelltitle command (and appropriate
escapes in the shell prompt). This only occurs for gnome-terminal and
xfce4-terminal (both based on the VTE widgit), and only with the current
repo sources, not in existing releases.

The bug is tracked at https://savannah.gnu.org/bugs/index.php?23699
There are a couple of scripts there that can be used to produce the problem.

After spending some significant time analyzing what's going on, it looks
like some combination of the use of CSR ("change scroll region") to set
up the hardstatus line, and then interspersing scrolls of the upper N-1
lines with updates of the final hardstatus line, causes the problem.
Screen is clearly not doing anything wrong, so the bug is VTE's.

However, the fact remains that previous versions of Screen would work,
whereas the current one doesn't. It turns out that the difference is,
release versions of Screen have always sent an "Erase Line" sequence
before re-drawing the status line, whereas the current source no longer
does that. This was probably to minimize any "flashing" that might be
seen as the status line is redrawn.

However, despite the fact that this is not our bug, it's still kind of
our problem, in that if we don't work around it, we'll have to direct
anyone who bumps into it how to deal with it (it can be worked around by
disabling scroll regions, forcing screen to use other means to handle
scrolls: "terminfo xterm* cs@"). So, I'm inclined to put the
line-erasure back in, to address this problem.

Any comments, thoughts?

- --
Micah J. Cowan
Programmer, musician, typesetting enthusiast, gamer,
and GNU Wget Project Maintainer.
http://micah.cowan.name/
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